How to send a custom Date Field via API #3

Hi, I have created a custom field in Date format.

How do I update this field to a contact via API? The field I'm trying to update is field [17].

Ex:

parameters = {
"contact": {
'phone': '999',
"field [17]": "2020-04-01T00: 00: 00-00: 00"
}
}
print ('I pass the parameters:' + str (parameters))
answer = ac_client.contacts.update_a_contact (idMarketing, parameters)